In the Home tab of your server console, go to the segment labeled "Server Command" and enter in /deop <username of the random guy> (to make them no longer an operator) then enter another command: /op <your username> (to re-op you). If they banned you as well do /unban <your username> or if you don't have the "Essentials" plugin you'll need to go to the File Manager tab, find the file called "banned-players.json" and delete the segment with your username. To try and undo the damage they did I'd recommend Contacting Minehut Support and request to have your world rolled back to before they ruined everything- otherwise in the future I'd recommend a plugin called "Core Protect" - which can be extremely helpful in undoing many things encase this ever happens again (It can't restore anything to a point before it was installed though- so it wouldn't be able to undo this)
Hope everything works out, and let me know if you have any problems.
(Also, before you try and undo any of the damage, I'd recommend trying to get in contact with a minehut staff- either by /msg to them in game, or via discord- and tell them about what happened as well as the usernames of the griefers, because it's against Minehut Rules to grief or destroy other peoples servers without their permission [rule #3]- and might be able to get those people banned from minehut so they can't grief anybody else's server in the future.)